1. Field of the Invention
The present invention relates generally to a system for propelling marine vessels. In particular, the invention relates to an auxiliary propulsion system for sail-powered marine vessels that uses a combined electric motor and transmission device having a continuously variable speed output, a stored energy supply for powering the device, and an electrical recharging system for recharging the stored energy supply.
2. Description of the Prior Art
Traditionally, numerous types of marine vessels have relied on the use of sails as their primary source of motive energy. However, for safety reasons, the larger classes of sail-powered vessels are typically equipped with auxiliary power sources for use during low wind conditions or for maneuvering in and out of harbors and slips. Such auxiliary power sources typically consist of internal combustion engines or electrically powered motors. Both of these power sources have inherent disadvantages as will be discussed below.
Internal combustion engines require constant maintenance and often become environmental hazards after extended use or inadequate maintenance. For example, internal combustion engines require the use of oil-based fuels and lubricants that can leak and emit unpleasant, unsightly and unsafe odors. In addition, internal combustion engines are comparatively loud, and often can become unreliable due to age or constant exposure to the saltwater and extreme weather conditions common to the environment of marine vessels. The necessary fuel system and engine block are bulky and add unwanted weight to marine vessels. Finally, any supply of fuels and lubricants on a marine vessel can occupy a considerable amount of a vessel's limited space, and also pose a fire hazard to the vessel and its occupants.
On the other hand, electric motors used in marine vessels are generally quieter, less polluting and require less maintenance than internal combustion engines. However, electric motors also suffer from a number of inherent problems. Electric motors are usually powered by batteries which cannot operate for extended periods of time without recharging. During normal operation, marine vessels are often far from shore and do not have a recharging source. Large banks of batteries may be employed to prolong the amount of time between battery rechargings. However, like the fuel tanks, the engine block and the required supplies for an internal combustion engine, the large banks of batteries needed to run conventional electric motors can be bulky and heavy.
A need exists, therefore, for an auxiliary propulsion system for marine vessels that is comparatively lightweight and dependable, occupies less space than the conventional auxiliary propulsion system, can operate for extended periods of time, and is not absolutely dependent on land-based facilities for replenishment of its energy supply.
Marine vessels are operated in environments having almost unlimited energy sources. For example, as noted above, sail-powered marine vessels use the wind as their primary motive power source. However, in addition to the wind, such vessels are typically exposed to several hours of direct sunlight, and are surrounded by water that is constantly in motion. The movement of vessels under sail by itself can generate the movement of water. The wind, sun and water offer sources of energy which could potentially help power marine vessels.
Consequently, a further need exists for a propulsion system for marine vessels that can harness the energies of the wind, sun or water to a greater degree than is possible in current conventional marine vessels.